Biofuel applications of botryococcene

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Botryococcenes are the major oil constituents of the green algae Botryococcus braunii. The hydrocarbons this species produces can be chemically converted into fuels. Transesterification can NOT be used to make biodiesel from botryococcenes, the major oil of Botryococcus braunii. This is because Botryococcene is not a 'vegetable oil' (which is a fatty acid triglyceride) but is instead a triterpene, and lacks the free oxygen for transesterification. It can be used as feedstock for hydrocracking in an oil refinery to produce octane (gasoline, a.k.a. petrol), kerosene, and diesel. Up to 86% of its dry weight can be long chain hydrocarbons.

There are several challenges which must be met in order to economically produce the desired alkanes such as gasoline. This will only be briefly covered in this article at this time, as it has only just begun.

First is that a suitable strain of Bb (Botryococcus braunii) must be found. Several strains are available from algae specimen banks, but there is no guarantee that these are high-producing strains. Some plant patent applications have been filed and patents granted, for high producing strains. It is within reason for even a small scale producer of boytrococcenes to breed successively higher producing strains of Bb, due to the reasonably fast generation rate. However, in selecting Bb strains for high Botryococcene production, it is likely that other beneficial attributes may be bred out. For instance, resistance to disease, competitive advantages against other organisms, and survivability in less than ideal climates. In this case, a photobioreactor may be needed.

The practice of farming algae is know as algaculture. However, there are properties of Botryococcus braunii which make its harvest a bit different than the harvest of other algae. Compared to other green algae species it has a relatively thick cell wall that is accumulated from previous cellular divisions; making extraction of cytoplasmic components rather difficult. Fortunately, much of the useful hydrocarbon oil is outside of the cell. This gives rise to the hope that the algae will not have to be killed in order to extract its useful oil. Indeed, this is the case. Several methods are available to extract the botryococcene. One that shows the most promise is the use of hexane as a solvent. If used at the proper molarity, it does not kill the majority of the Bb, while extracting the botryococcene. However, like all organisms Bb is less productive in old age. It is said the become 'senescent' and produce less boytococcene. It will eventually die of old age. However, some algae farmers may wish to weed out these non-producing algae and not return them to the photobioreactor.